Superconducting Quantum Interference Device Loop Research Articles

On the coupling of magnetic moments to superconducting quantum interference devices

We investigate the coupling factor φ µ that quantifies the magnetic flux Φ per magnetic moment µ of a point-like magnetic dipole that couples to a superconducting quantum interference device (SQUID). Representing the dipole by a tiny current-carrying (Amperian) loop, the reciprocity of mutual inductances of SQUID and Amperian loop provides an elegant way of calculating ϕμ(r,eˆμ) vs. position r and orientation eˆμ of the dipole anywhere in space from the magnetic field BJ(r) produced by a supercurrent circulating in the SQUID loop. We use numerical simulations based on London and Ginzburg–Landau theory to calculate φ µ from the supercurrent density distributions in various superconducting loop geometries. We treat the far-field regime ( r≳a= inner size of the SQUID loop) with the dipole placed on (oriented along) the symmetry axis of circular or square shaped loops. We compare expressions for φ µ from simple filamentary loop models with simulation results for loops with finite width w (outer size A > a), thickness d and London penetration depth λ L and show that for thin ( d≪a ) and narrow (w < a) loops the introduction of an effective loop size aeff in the filamentary loop-model expressions results in good agreement with simulations. For a dipole placed right in the center of the loop, simulations provide an expression ϕμ(a,A,d,λL) that covers a wide parameter range. In the near-field regime (dipole centered at small distance z above one SQUID arm) only coupling to a single strip representing the SQUID arm has to be considered. For this case, we compare simulations with an analytical expression derived for a homogeneous current density distribution, which yields excellent agreement for λL>w,d . Moreover, we analyze the improvement of φ µ provided by the introduction of a narrow constriction in the SQUID arm below the magnetic dipole.

Increasing linear flux range of SQUID amplifier using self-feedback effect

Superconducting quantum interference devices (SQUIDs) are low-noise amplifiers that are essential for the readouts of translation edge sensors (TESs). The linear flux range is an important parameter for SQUID amplifiers, especially those controlled by high-bandwidth digital flux-locked-loop circuits. A large linear flux range conduces to accurately measuring the input signal and also increasing the multiplexing factor in the time-division multiplexed (TDM) readout scheme of the TES array. In this work, we report that the linear flux range of an SQUID can be improved by using self-feedback effect. When the SQUID loop is designed to be asymmetric, a voltage-biased SQUID shows an asymmetric current–flux (I–Φ) response curve. The linear flux range is improved along the I–Φ curve with a shallow slope. The experimental results accord well with the numerical simulations. The asymmetric SQUID will be able to serve as a building block in the development of the TDM readout systems for large TES arrays.

Measurements of Phase Dynamics in Planar Josephson Junctions and SQUIDs.

We experimentally investigate the stochastic phase dynamics of planar Josephson junctions (JJs) and superconducting quantum interference devices (SQUIDs) defined in epitaxial InAs/Al heterostructures, and characterized by a large ratio of Josephson energy to charging energy. We observe a crossover from a regime of macroscopic quantum tunneling to one of phase diffusion as a function of temperature, where the transition temperature T^{*} is gate-tunable. The switching probability distributions are shown to be consistent with a small shunt capacitance and moderate damping, resulting in a switching current which is a small fraction of the critical current. Phase locking between two JJs leads to a difference in switching current between that of a JJ measured in isolation and that of the same JJ measured in an asymmetric SQUID loop. In the case of the loop, T^{*} is also tuned by a magnetic flux.

Mechanical frequency control in inductively coupled electromechanical systems

Nano-electromechanical systems implement the opto-mechanical interaction combining electromagnetic circuits and mechanical elements. We investigate an inductively coupled nano-electromechanical system, where a superconducting quantum interference device (SQUID) realizes the coupling. We show that the resonance frequency of the mechanically compliant string embedded into the SQUID loop can be controlled in two different ways: (1) the bias magnetic flux applied perpendicular to the SQUID loop, (2) the magnitude of the in-plane bias magnetic field contributing to the nano-electromechanical coupling. These findings are quantitatively explained by the inductive interaction contributing to the effective spring constant of the mechanical resonator. In addition, we observe a residual field dependent shift of the mechanical resonance frequency, which we attribute to the finite flux pinning of vortices trapped in the magnetic field biased nanostring.

A second-order gradiometric superconducting quantum interference device current sensor with cross-coupled structure

Superconducting quantum interference device (SQUID) has extremely high magnetic field sensitivity, current sensitivity, and can detect a low-noise weak current signal. The SQUID current sensor has become the only option of the readout of low-noise detector, such as transition-edge sensor (TES). In this paper, a second-order gradiometric cross-coupled SQUID current sensor for TES application is developed. According to the requirements for TES detectors, the structure and various parameters of SQUID current sensor are designed. The SQUID loop, input coil and feedback coil of the SQUID current sensor all use the second-order gradiometric structure. All the couple ways between SQUID loop and input coil or feedback coil adopt cross-coupling mode in different planes, which can effectively weaken the parasitic capacitance. A second-order gradiometric cross-coupled SQUID current sensor based on Nb/Al-AlO&lt;i&gt;&lt;sub&gt;x&lt;/sub&gt;&lt;/i&gt;/Nb Josephson junction is successfully fabricated on a silicon wafer by optimizing the process. The properties of the second-order gradiometric cross-coupled SQUID current sensor are measured at liquid helium temperature. The bias current of SQUID is 215 μA when the modulation depth of &lt;i&gt;V&lt;/i&gt;-&lt;i&gt;Φ&lt;/i&gt; modulation curve is maximum. The maximum modulation peak of SQUID is 31 μV. The flux-to-voltage transfer coefficient of SQUID is 108 μV/&lt;i&gt;Φ&lt;/i&gt;&lt;sub&gt;0&lt;/sub&gt;. The input coil current sensitivity is 17 μA/&lt;i&gt;Φ&lt;/i&gt;&lt;sub&gt;0&lt;/sub&gt;, the mutual inductance between SQUID loop and input coil is 117 pH. The current sensitivity of feedback coil is 86 μA/&lt;i&gt;Φ&lt;/i&gt;&lt;sub&gt;0&lt;/sub&gt;, the mutual inductance between SQUID loop and feedback coil is 23 pH. The second-order gradiometric cross-coupled SQUID current sensor has a white flux noise of 2 μ&lt;i&gt;Φ&lt;/i&gt;&lt;sub&gt;0&lt;/sub&gt;/&lt;inline-formula&gt;&lt;tex-math id="M3"&gt;\begin{document}$ \sqrt{{\rm{H}}{\rm{z}}} $\end{document}&lt;/tex-math&gt;&lt;alternatives&gt;&lt;graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="12-20201816_M3.jpg"/&gt;&lt;graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="12-20201816_M3.png"/&gt;&lt;/alternatives&gt;&lt;/inline-formula&gt; and a white current noise of 34 pA/&lt;inline-formula&gt;&lt;tex-math id="M4"&gt;\begin{document}$ \sqrt{{\rm{H}}{\rm{z}}} $\end{document}&lt;/tex-math&gt;&lt;alternatives&gt;&lt;graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="12-20201816_M4.jpg"/&gt;&lt;graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="12-20201816_M4.png"/&gt;&lt;/alternatives&gt;&lt;/inline-formula&gt; with 1/&lt;i&gt;f&lt;/i&gt; corner frequency around 200 Hz. The result of noise level under the condition without magnetic shielding shows that the SQUID current sensor with second-order gradiometric cross-coupled structure has an excellent capability of weakening the environmental electromagnetic interference. In the future, we will further improve the mutual inductance of the second-order gradiometric cross-coupled SQUID current sensor between SQUID loop and input coil, optimize the size and critical current of Josephson junction, in order to improve the input sensitivity of SQUID device, reduce the current noise level and the 1/&lt;i&gt;f&lt;/i&gt; corner frequency, and meet more requirements for TES applications.

Superconducting quantum interference devices made of Sb-doped Bi2Se3 topological insulator nanoribbons

We report the fabrication and characterization of superconducting quantum interference devices (SQUIDs) made of Sb-doped Bi2Se3 topological insulator (TI) nanoribbon (NR) contacted with PbIn superconducting electrodes. When an external magnetic field was applied along the NR axis, the TI NR exhibited periodic magneto-conductance oscillations, the so-called Aharonov-Bohm oscillations, owing to one-dimensional subbands. Below the superconducting transition temperature of PbIn electrodes, we observed supercurrent flow through TI NR-based SQUID. The critical current periodically modulates with a magnetic field perpendicular to the SQUID loop, revealing that the periodicity corresponds to the superconducting flux quantum. Our experimental observations can be useful to explore Majorana bound states (MBS) in TI NR, promising for developing topological quantum information devices.

Investigation of Large Coupling Between TES X-Ray Microcalorimeter and Microwave Multiplexer Based on Microstrip SQUID

We report on the study of a microwave superconducting quantum interference device (SQUID) multiplexer (MW-Mux) with current noise lower than that of our typical transition-edge sensor (TES) X-ray microcalorimeter. A large mutual inductance, between SQUID loop and input inductor connected to a TES X-ray microcalorimeter in series, realizes such low current noise referred to the SQUID input, but also can cause undesirable resonances which affect the SQUID performances. In this paper, we have developed the MW-Mux with mutual inductance of about 370 pH, which is six times larger than that of the previous one, by adopting a spiral input coil longer than a half wavelength at the readout microwave frequency. Its characteristics are evaluated, and the results have shown that the distortion of the SQUID characteristics and the degradation of its noise performance are not clearly observed. Finally, we have developed an MW-Mux microstrip SQUID with a low current noise of <; 20 pA/√(Hz) which is below the typical noise of our TES X-ray microcalorimeter, 30 pA/√(Hz).

Evaluation of Josephson Junction Parameter Dispersion Effects in Arrays of HTS SQUIDs

We report on the experimental evaluation of dispersion effects on superconducting quantum interference device (SQUID) arrays made with high-temperature superconductor technology. The dispersion of Josephson junction parameters not only results in different operational temperature ranges but also in a flux shift of the voltage versus flux response of the SQUID. Another contribution to the phase shift originates from unbalanced inductances of each branch of the SQUID loop. Measurements show that both contributions can be discriminated. Optimal operation of SQUID arrays is obtained in principle only when these self-induced fluxes are negligible. Degradation of the response is more important when the involved currents are larger, i.e., at lower temperature. We compensated these phase shifts for an array of a few SQUIDs connected in series by direct current injection in one of the branches of each SQUID, thereby recovering the characteristic “antipeak” response. This demonstrates that in the lower temperature range of SQUID operation, phase shifts are mainly responsible for the degradation of the SQUID array response.

Inductance analysis of superconducting quantum interference devices with 3D nano-bridge junctions

Superconducting quantum interference devices (SQUIDs) with 3D nano-bridge junctions can be miniaturized into nano-SQUIDs that are able to sense a few spins in a large magnetic field. Among all device parameters, the inductance is key to the performance of SQUIDs with 3D nano-bridge junctions. Here, we measured the critical-current magnetic flux modulation curves of 12 devices with three design types using a current strip-line directly coupled to the SQUID loop. A best flux modulation depth of 71% was achieved for our 3D Nb SQUID. From the modulation curves, we extracted the inductance values of the current stripe-line in each design and compared them with the corresponding simulation results of InductEX. In this way, London penetration depths of 110 and 420 nm were determined for our Nb (niobium) and NbN (niobium nitride) films, respectively. Furthermore, we showed that inductances of 11 and 119 pH for Nb and NbN 3D nano-bridge junctions, respectively, dominated the total inductance of our SQUID loops which are 23 pH for Nb and 255 pH for NbN. A screening parameter being equal to one suggests optimal critical currents of 89.6 and 8.1 μA for Nb and NbN SQUIDs, respectively. Additionally, intrinsic flux noise of 110 ± 40 nΦ0/(Hz)1/2 is calculated for the Nb SQUIDs with 3D nano-bridge junctions by Langevin simulation.

Entanglement of quantum node based on hybrid system of diamond nitrogen-vacancy center spin ensembles and superconducting quantum circuits

Quantum entanglement is a kernel of quantum computation and quantum communication. We introduce a theoretical scheme to achieve the entanglement between two separated quantum nodes in a hybrid system. The proposed hybrid system based on diamond nitrogen-vacancy (NV) center spin ensemble is coherently coupled to a superconducting quantum circuit consisting of two quantum nodes and a quantum channel. Each node in our setup is composed of an NV center spin ensemble magnetically coupled to a superconducting coplanar resonator. The NV center spin ensemble composed of N identical and non-interacting NV spins, is placed in the magnetic field antinode of the superconducting coplanar resonator where the coupling is maximized. An array of superconducting quantum interference devices (SQUIDs) is inserted in the central conductor of resonator to make its frequency tunable with the magnetic flux threading through the SQUID loops. This flux is generated by passing current through an on-chip wire, so that the resonator can be brought in resonance with the NV center spins without changing their Zeeman splitting. Quantum qubits encoded into two separate nodes are connected by a vacuum superconducting coplanar resonator that is used as a quantum channel. This setup can potentially take the best elements of each individual system:NV center spin ensemble with longer coherence time capable of preparing, storing and releasing photonic quantum information, and the superconducting quantum circuits are easy to manipulate externally and can perform quantum logic gates to control quantum information rapidly. In order to realize the entanglement between two separated quantum nodes, firstly, we make a canonical transformation and obtain the Hamiltonian of the system that is reduced to two NV center spin ensembles resonantly coupled to a single mode of the superconducting coplanar resonator. Then we put forward the hybrid NV center spin-photon qubit encoding. In this hybrid encoding, the NV center spin and photon degrees of freedom enter on an equal footing into the definition of the qubit, in which case, quantum channel will switch on when three superconducting coplanar resonators are in resonance with each other, and all the manipulations can perform simply by tuning the frequencies of the superconducting coplanar resonators. Under the precise control of the evolution time, high fidelity entanglement between two separated quantum nodes is achieved. We show that this proposal can provide high fidelity quantum entanglement under realistic conditions, both in the resonant and the dispersive interaction cases. This hybrid quantum system will exhibit long coherence time and possess features like easy fabrication, integratability, and potential scalability. Furthermore, the quantum node composed of an NV center spin ensemble magnetically coupled to a superconducting coplanar resonator can be respectively integrated, which has practical applications in the realization of quantum information transmission and quantum entanglement among multiple quantum nodes.

Improved coupling of nanowire-based high-Tc SQUID magnetometers—simulations and experiments

Superconducting quantum interference devices (SQUIDs) based on high critical-temperature superconducting nanowire junctions were designed, fabricated, and characterized in terms of their potential as magnetometers for magnetoencephalography (MEG). In these devices, the high kinetic inductance of junctions and the thin film thickness (50 nm) pose special challenges in optimizing the field coupling. The high kinetic inductance also brings difficulties in reaching a low SQUID noise. To explore the technique for achieving a high field sensitivity, single-layer devices with a directly connected pickup loop and flip-chip devices with an inductively coupled flux transformer using a two-level coupling approach were fabricated and tested. Two-level coupling is an approach designed for flip-chip nanowire-based SQUIDs, in which a washer type SQUID pickup loop is introduced as an intermediate coupling level between the SQUID loop and the flux transformer input coil. The inductances and effective areas of all these devices were simulated. We found that at T = 77 K, flip-chip devices with the two-level coupling approach (coupling coefficient of 0.37) provided the best effective area of 0.46 mm2 among all the tested devices. With a flux noise level of 55 0 , the field sensitivity level was 240 fT . This sensitivity is not yet adequate for MEG applications but it is the best level ever reached for nanowire-based high-Tc SQUID magnetometers.

3D nanoSQUID based on tunnel nano-junctions with an energy sensitivity of 1.3 h at 4.2 K

We report the performance of a reliable three-dimensional nanometer-sized Superconducting QUantum Interference Device (SQUID). The use of superconductor-isolator-superconductor Nb/Al-AlOx/Nb Josephson tunnel junctions together with small SQUID loop dimensions permits a high modulation depth of the SQUID's critical current and thus leads to very low intrinsic flux noise of the device. In particular, we present electrical characterization including detailed noise investigations. At 4.2 K, two-stage noise measurements with a SQUID as a low noise preamplifier result in a white flux noise of 51 nΦ0/Hz1/2, which is equivalent to an energy resolution of 1.3 h, with h being Planck's constant. Simulation of spin sensitivities results in about 1 μB/Hz1/2 for an electron spin positioned directly above the SQUID ring.

Feedback solutions for low crosstalk in dense arrays of high-Tc SQUIDs for on-scalp MEG

Magnetoencephalography (MEG) systems based on a dense array of high critical temperature (high-Tc) superconducting quantum interference devices (SQUIDs) can theoretically outperform a state-of-the-art MEG system. On the way towards building such a multichannel system, we evaluate feedback methods suitable for use in dense high-Tc SQUID arrays where the sensors are in very close proximity to the head (on-scalp MEG). We test on-chip superconducting coils and direct injection of the feedback current into the SQUID loop as alternatives to the wire-wound copper coils commonly used in single-channel high-Tc SQUID-based MEG systems. For the evaluation, we have performed coupling, noise, and crosstalk measurements. We conclude that direct injection is the optimal solution for dense on-scalp MEG as it gives crosstalk below 0.5% even between SQUIDs whose pickup loops are within 0.8 mm of one another. Further, this solution provides sufficient flux coupling without adding additional noise. Finally, it does not compromise the standoff distance, which is important for on-scalp MEG.

High-Tc Step-Edge Josephson Junction Arrays: Comparison of Simulated and Experimental Voltage Responses

With the recent development of multijunction superconducting quantum interference device (SQUID) arrays and superconducting quantum interference filters (SQIFs) using high-temperature superconducting (HTS) materials, it has become increasingly desirable to accurately model HTS devices to enable the optimization of the design for enhanced performance before fabrication. Initially, to develop our simulation capability for HTS devices, we have been working with a commercial software package to fit the data obtained from the characterization of two HTS devices. The models were iteratively adjusted by increasing the number of parameters taken into account, including the aspect ratio of the SQUID loop and the bias injection point. These models were developed for devices fabricated using YBCO step-edge junctions formed on MgO substrates. It was found that the biasing mechanism affects the SQIF voltage response to applied magnetic fields. This has implications for the design of larger arrays.

Low Noise NanoSQUIDs Based on Deep Submicron Josephson Tunnel Junctions

In the recent years, it has been shown that the magnetic response of nano-objects (nanoparticles, nanobeads, and small cluster of molecules) can be effectively measured by using a Superconducting Quantum Interference Device (SQUID) with a small sensitive area. Here, we present high sensitivity nanoSQUIDs based on deep submicrometer Josephson tunnel junctions fabricated by a Focused Ion Beam (FIB) sculpting method. Two different configuration have been realized: a vertical configuration where the nanosensor loop is perpendicular to the substrate plane and a planar one having the SQUID loop parallel to the substrate plane. In both configurations the flux capture and the junction areas are 0.2 and 0.09 μm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> , respectively. At liquid helium temperature the nanosensor have shown non-hysteretic current-voltage characteristics and large voltage modulation depths as well as high voltage responsivities. A spectral density of magnetic flux noise as low as 700 nΦ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> /Hz <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1/2</sup> has been measured in small signal mode using a low noise direct coupling electronics. The computed spin sensitivity has provided a value less than 10 Bohr magneton per bandwidth unit.

Optimizing the spin sensitivity of grain boundary junction nanoSQUIDs—towards detection of small spin systems with single-spin resolution

We present an optimization study of the spin sensitivity of nano superconducting quantum interference devices (SQUIDs) based on resistively shunted grain boundary Josephson junctions. In addition the direct current SQUIDs contain a narrow constriction onto which a small magnetic particle can be placed (with its magnetic moment in the plane of the SQUID loop and perpendicular to the grain boundary) for efficient coupling of its stray magnetic field to the SQUID loop. The separation of the location of optimum coupling from the junctions allows for an independent optimization of the coupling factor and junction properties. We present different methods for calculating (for a magnetic nanoparticle placed 10 nm above the constriction) as a function of device geometry and show that those yield consistent results. Furthermore, by numerical simulations we obtain a general expression for the dependence of the SQUID inductance on geometrical parameters of our devices, which allows to estimate their impact on the spectral density of flux noise of the SQUIDs in the thermal white noise regime. Our analysis of the dependence of and on the geometric parameters of the SQUID layout yields a spin sensitivity of a few ( is the Bohr magneton) for optimized parameters, respecting technological constraints. However, by comparison with experimentally realized devices we find significantly larger values for the measured white flux noise, as compared to our theoretical predictions. Still, a spin sensitivity on the order of for optimized devices seems to be realistic.

Superconducting quantum interference device microsusceptometer balanced over a wide bandwidth for nuclear magnetic resonance applications.

Superconducting Quantum Interference Device (SQUID) microsusceptometers have been widely used to study magnetic properties of materials at microscale. As intrinsically balanced devices, they could also be exploited for direct SQUID-detection of nuclear magnetic resonance (NMR) from micron sized samples, or for SQUID readout of mechanically detected NMR from submicron sized samples. Here, we demonstrate a double balancing technique that enables achievement of very low residual imbalance of a SQUID microsusceptometer over a wide bandwidth. In particular, we can generate ac magnetic fields within the SQUID loop as large as 1 mT, for frequencies ranging from dc up to a few MHz. As an application, we demonstrate direct detection of NMR from (1)H spins in a glycerol droplet placed directly on top of the 20 μm SQUID loops.

Many-body interactions with tunable-coupling transmon qubits.

The efficient implementation of many-body interactions in superconducting circuits allows for the realization of multipartite entanglement and topological codes, as well as the efficient simulation of highly correlated fermionic systems. We propose the engineering of fast multiqubit interactions with tunable transmon-resonator couplings. This dynamics is obtained by the modulation of magnetic fluxes threading superconducting quantum interference device loops embedded in the transmon devices. We consider the feasibility of the proposed implementation in a realistic scenario and discuss potential applications.

Light-superconducting interference devices

Recently, we have proposed the half-Josephson laser (HJL): a device that combines lasing with superconducting leads, providing a locking between the optical phase and the superconducting phase difference between the leads. In this work, we propose and investigate two setups derived from a superconducting quantum interference device (SQUID), where two conventional Josephson junctions are replaced by two HJLs. In the first setup, the HJLs share the same resonant mode, while in the second setup two separate resonant modes of the two lasers are coupled optically. We dub the setup ``light-superconducting interference device'' (LSID). In both setups, we find the operating regimes similar to those of a single HJL. Importantly, the steady lasing field is significantly affected by the magnetic flux penetrating the SQUID loop, with respect to both amplitude and phase. This provides opportunities to tune or even quench the lasing by varying a small magnetic field. For the second setup, we find a parameter range where the evolution equation for the laser fields supports periodic cycles. The fields are thus modulated with the frequency of the cycle resulting in an emission spectrum consisting of a set of discrete modes. From this spectrum, two modes dominate in the limit of strong optical coupling. Therefore, the LSID can be also used to generate such modulated light.

Fabrication of Arrays of Nano-Superconducting Quantum Interference Devices Using a Double-Angle Processing Approach

Arrays of superconducting quantum interference devices (SQUIDs) from high-temperature superconductors such as YBCO have been shown to significantly improve the signal-to-noise ratio when compared to single SQUIDs from high- <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">T</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">C</sub> material. This is based on the finding that the voltage response of a current biased array increases by the number of SQUID loops <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">N</i> , while the noise only increases as <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">N</i> <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1/2</sup> . It is therefore desirable to fabricate array structures with as many SQUIDs placed in series as possible. We present a fabrication technique for SQUID arrays based on ion-damage Josephson Junctions (JJ) that allows for creating virtually any SQUID-array design on any thin-film superconducting materials such as YBCO or MgB <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> . The fabrication employs electron beam lithography (EBL) to write the SQUID-array, electrical contact pads and JJ fine lines in a single lithography step. It is performed on a thick trilayer structure that allows for high-aspect ratio features. The superior resolution of EBL makes SQUID loop diameters down to a few hundred nanometers possible. Subsequent high-energy ion-implantation creates the JJ. Using low-energy argon ion milling at an angle to the sample shadows the fine lines used for creation of the JJ and transfers the EBL-defined SQUID-array and electrical contact pads into the thin-film superconductor.